Dust suppressor for rotary drills

ABSTRACT

A ROTARY DRILLING RIG FOR USE IN DRILLING BLAST HOLES FOR THE REMOVAL OF ORE. THE RIG INCLUDES A VERTICALLY DISPOSED ROTATABLE SHAFT, THE LOWER END OF WHICH CARRIES A PLURALITY OF ROTARY CUTTER BITS THAT ENGAGE AND GRIND THE ORE SURFACE. THE SHAFT CARRIES A COMPRESSED AIR PASSAGE WHICH OPENS AT THE LOWER END TO BLOW ROCK BITS AND DUST UPWARDLY FROM THE BLAST HOLE, AND A SEPARATE WATER PASSAGE WHICH DISTRIBUTES WTER RADIALLY OUTWARD FROM THE SHAFT AT A POINT ABOVE THE CUTTERS TO SUPPRESS THE DUST BEFORE REACHING THE GROUND SURFACE.

vSept. 20, 1971 G. E. LEHTINEN 3,605,913

DUST SUYPRESSOR FOR ROTARY DRILLS Filed April 14, 1970 2 Sheets-Shoat 1 INVENTOR. GERALD E. LEHr/NE/v AT TORNEYS p 20, 1971 s. E. LEHTINEN DUST SUPPRESSOR FOR ROTARY DRILLS 2 Sheets-Shoot 8 Filed April 14, 1970 .m m mm W m wp m6o L 4 T MM V E a B x United States Patent 3,605,913 DUST SUPPRESSOR FOR ROTARY DRILLS Gerald E. Lehtinen, Salt Lake City, Utah, assignor to Reserve Mining Company, Silver Bay, Minn. Filed Apr. 14, 1970, Ser. No. 28,395 Int. Cl. E21b 21/04; E21c 7/06 US. Cl. 173-74 6 Claims ABSTRACT OF THE DISCLOSURE A rotary drilling rig for use in drilling blast holes for the removal of ore. The rig includes a vertically disposed rotatable shaft, the lower end of which carries a plurality of rotary cutter bits that engage and grind the ore surface. The shaft carries a compressed air passage which opens at the lower end to blow rock bits and dust upwardly from the blast hole, and a separate water passage which distributes water radially outward from the shaft at a point above the cutters to suppress the dust before reaching the ground surface.

The invention is related to rotary drilling rigs used for making blast holes in the process of mining and ore removal, and specifically contemplates apparatus for suppressing dust resulting from such operations.

One method of surface mining extremely hard ore consists of drilling a blast hole to a predetermined depth, filling the hole with an explosive and detonating the explosive with subsequent removal of the loosened rock. The drilling of such blast holes is often carried out by a rotary drilling rig having a vertically disposed rotary drilling shaft the lower end of which carries a plurality of freely rotating, carbide-tipped cutter bits. As the drilling shaft is rotated and lowered, the cutter bits engage and grind the ore surface, creating the hole while leaving bits of rock and dust. This residual material is removed by application of highly compressed air at the cutting surface, which is supplied through a bore in the drilling shaft. The rock bits and dust are thus blown upwardly out of the hole for deposit at the ground surface surrounding the drilling rig.

Two significant problems are encountered by creating blast holes in this manner. First, although tipped with extremely hard material, the rotary bits wear relatively fast and must be continually replaced. Second, the vast quantity of dust and rock bits brought to the ground surface by compressed air gives rise to a severely dusty environment which is both hazardous to the health of persons operating the drill rig and damaging to the moving parts of the drill rig.

Several schemes have been used in solving the latter problem, one of which is attempting to capture the dust as it reaches the ground surface. Such attempts have not met with great success. A second solution to the problem has been injection of Water into the hollow drilling shaft which is mixed with the compressed air and introduced at the hole bottom. The water-air mixture picks up a portion of the drilling residue and carries it up the hole to the ground surface. However, the remaining mixture forms a slurry with the residue at the hole bottom which results in regrinding of cuttings and increased wear of the rotary bits. For reasons not clearly understood, the water-air mixture passing through the rotary bit bearings also causes spalling of the bearing surfaces which results in reduced bearing life. Thus, although this method suppresses virtually percent of the dust generated by the drilling process, its usefulness is minimal due to the substantially increased bit wear.

Thus, dry hole drilling proves to be more economical, but with the great disadvantage of an extremely dusty environment; and satisfactory dust suppression through known methods greatly increases cost of the drilling itself.

My invention is the result of an attempt to determine a more feasible approach to dust suppression for such drilling rigs without increasing the wear rate of the rotary cutter bits. In the preferred embodiment, it consists of an insert which becomes an integral part of the drilling shaft or stem and is disposed at a point above the rotary cutter bits. The insert includes a plurality of radially directed conduits which open on the outer face of the insert. The several conduits are commonly connected by means of a manifold to a water hose which extends upwardly through the drilling shaft and into the drive head of the drill by means of a swivel joint. Another water hose joins the swivel joint to the drill pump, which supplies water under pressure.

The openings on the insert surface are arranged so that water is distributed radially outward. The size of the openings, volume of water and water pressure are chosen to effect sprinkling or spraying as the drill shaft rotates. Thus, the rock cuttings and dust which are forced upward through the hole by compressed air begin mixing with the sprayed water. This mixing action continues as the cuttings continue upward through the hole, resulting in the deposit of dust-free but damp rock cuttings at the ground surface surrounding the hole.

The feature of primary significance is providing the water spray at a point above the rotary cutting bits which gives rise to full dust suppression without creating a slurry at the bottom of the hole. Thus, full dust suppression is effected while completely dry drilling continues.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front elevational view of a drilling rig embodying the inventive principle.

FIG. 2 is an enlarged sectional view of the rotary drilling head and a portion of the drilling shaft of the drilling rig, taken along the line 22 of FIG. 1

FIG. 3 is an enlarged sectional view of the lower end of the drilling shaft including cutting bits, stabilizing rollers and dust suppressors, taken along the line 3-3 of FIG. 1;

FIG. 4 is an enlarged partial sectional view of a manifold used in the dust suppressor, taken along the line 4-4 of FIG. 3;

FIG. 5 is a sectional view of the drilling shaft in dicating an upper support member for the dust suppressor, taken along the line 55 of FIG. 3;

FIG. 6 is a further enlarged sectional view of the drilling head, taken along the line 66 of FIG. 2; and

FIG. 7 is a fragmentary sectional view of the drilling head, ta-ken generally along the irregular line 7-7 of FIG. 6.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 discloses a movable drilling rig represented generally by the numeral 11, which includes hydraulic front jacks 12 and rear jacks 13 for leveling and stabilization during operation. A drilling head represented generally at 14 rotatably drives a drilling shaft 15 by a pair of hydraulic motors 16 which receive a continuous sup ply of hydraulic fluid from lines 17. A flexible conduit 18 carrying compressed air is also connected to drilling head 14 for a purpose described in detail below.

Vertical traverse of drilling head 14, shaft 15, hydraulic lines 17 and compressed air line 18 is accomplished through use of a pair of high strength roller chains (not shown) connected to either side of the drilling head 14, which is slidably retained in a mast 1?. The roller chains are each driven by a sprocket carried on the shaft of a hydraulic motor mounted at the base of mast 19 (not shown).

A second pair of high strength chains 23 pass over a pair of pulleys 24 and attach to a drill table to pull down on mast 19 and maintain it in a state of tension.

A guide 25 is slidably retained by main guide members of mast 19, and is automatically positioned between drilling head 14 and drill table 20 by a steel cable and sleeve arrangement (not shown) to maintain vertical alignment of shaft 15.

The controls for drilling rig 11 are housed in an operators cab 26, and power is supplied for the several functions by a plurality of power plants in a protective housing 27.

Referring additionally to FIG. 2, drilling shaft 15 is shown to consist of a plurality of lengths each of which includes threaded connections at top and bottom for insertion or removal to vary the length of shaft 15. The uppermost length of shaft 15 is connected to the lower rotating portion of drilling head 14 as shown. The entire rotating portion of drilling head 14 is carried by an annular upper raceway 28 and lower raceway 129 which ride on individual sets of tapered bearings 31 and 32, respectively.

The enlarged sectional view of FIG. 6 shows the upper rotating end of drilling head 14, terminating in a hearing sleeve 33 which rotates against packing 34. The rotating unit is held in place by a threaded takeup nut 35 which bears against upper raceway 28 and rotates against a stationary oil seal 36. A locking pin 37 is inserted through the assembly and takeup nut 35 with the outer ends bent as shown to prevent its vibrating from place.

Rotary motion is imparted to shaft 15 by the two hydraulic motors 16 mentioned above, each of which drives a pinion gear (not shown) arranged in driving engagement with a bull gear 38. Gear 38 is keyed to the top end of shaft 15 and held against axial movement thereon by a retainer ring 39.

Referring to FIG. 3, the lower end of drilling shaft 15 carries a tri-cone rotary bit consisting of three freely rotatable cutter wheels 41 (two of which are shown) each of which includes sintered tungsten carbide inserts placed in concentric configurations on the cutter shell cone matrix. Cutter wheels 41 are mounted in a combination of journal, ball and roller bearings, none of which are shown.

Immediately above the tri-cone rotary bit on the outer surface of drilling shaft 15 are disposed three equidistantly-spaced rollers 42 (two of which are seen) each of which has a plurality of sintered tungsten carbide studs affixed to its surface. Rollers 42 stabilize the lower portion of drilling shaft 15 by riding on the hole wall, and maintain alignment throughout drilling operations.

Referring to both FIG. 2 and FIG. 3, it may be seen that a bore or passage 43 extends both through the rotating portion of drilling head 14 and drilling shaft 15, communicating at its upper end with a branch 44 of the compressed air passage 18 (which is carried by brackets 45 fastened to the stationary portion of drilling head 14), and opening at the lowermost end of drilling shaft 15. Bore 43 also communicates with an internal passage within the bearing pin of roller 42 by means of a small passage 46. The primary portion of compressed air passing through bore 43 is diffused between the cutter wheels 41 to serve as an upward air blast for removal of the loosened cuttings at the bottom of the drill hole. A portion of the compressed air is diverted to cool and clean the bearings of both cutter wheels 41 and rollers 42.

Referring specifically to FIG. 3, part of the overall length of drilling shaft 15 is formed by a shorter length or insertion member 51 which includes similar threaded connections. Extending through the bore portion 43 of length 51 is a conduit 52 supported at its upper end by a cross-support member 53 and terminating in a swivel coupling 54 (see also FIG. 5). The lower end of conduit 52 communicates with a spider manifold 55 (see also FIG. 4) the outer ends of which terminate in openings 56 on the surface of length 51.

Referring additionally to FIGS. 2 and 6, a length of hose 57 is connected to conduit 52 by means of swivel connection 54. Hose 57 may consist of a plurality of individual sections connected by couplings 58 in order to provide a length appropriate to the overall length of drilling shaft 15. Hose 57 extends upward through drilling head 14 and is connected to a non-rotating length of conduit 59 by means of a swivel coupling 61. Conduit 59 leaves the compressed air passage 44 through a sealed passageway 62 and is connected by appropriate means to a source of water under pressure, not shown.

In operation, a blast hole is formed by rotation of drill shaft 15 with cutter wheels 41 brought into grinding engagement with the ground surface, coupled with progressive downward movement of shaft 15 through operation of winch 21. Engagement of rollers 42 with the sides of the blast hole (FIG. 3) stabilizes the drilling operation and maintains drilling shaft 15 in vertical alignment.

Compressed air received through branch passage 44 and bore 43 of drilling shaft 15 is diffused at the bottom of the blast hole, forcing the cuttings and dust upward. Rotation of drilling shaft 15 causes hose 57 and manifold 55 to rotate, giving rise to a radially outward sprinkle or spray that mixes with the cutting residue as it passes upward. This mixture continues as the cuttings move upward, suppressing the dust and resulting in a deposit of damp cuttings at ground level (see FIG. 1). The bottom of the blast hole is kept dry, thus maintaining the most economical operation in terms of cost per foot drilled.

What is claimed is:

1. In rotary drilling apparatus including a plurality of sealably connectable lengths defining a rotatable shaft the extreme end of which carries bit means for forming a bore hole in material to be drilled, each of said connectable lengths having a longitudinal bore formed therein, the bores together defining a passage for communicating air under pressure to the extreme end of the rotatable shaft to remove residual material from the bore hole, the improvement comprising:

an insertion member sealably connected between two of said lengths at a point remote from said bit means, said insertion member having a bore formed therein for registration with said air passage and including means for distributing liquid radially outward therefrom into the bore hole to mix with the upwardly moving residual material;

and conduit means disposed in said air passage for connecting said liquid distributing means with a source of liquid under pressure.

2. The apparatus as defined by claim 1, wherein the conduit means further comprises swivel coupling means for rotatable connection to the source of liquid under pressure.

3. The apparatus as defined by claim 1, wherein the liquid distributing means comprises:

a plurality of openings radially disposed in the outer surface of the insertion member;

and a manifold having an inlet connectable with the conduit means and a plurality of outlets respectively communicating with said radially disposed openings. 4'. The apparatus as defined by claim 1, wherein the conduit means comprises a purality of 'sealably connectable conduit sections, each connectable link having a conduit section. T

5. The apparatus as defined by claim 1, wherein the conduit means further comprises swivel coupling means for rotatably connecting the conduit means to the liquid distributing means.

6. The apparatus as defined by claim 1, wherein the conduit is flexible.

References Cited UNITED STATES PATENTS 6/1938 Hawkins 175-215 10/1962 Thompson 175-320 10/1964 Grable 175215 8/1965 Madson 17569 US. Cl. X.R. 

